Removed IO_Options. No longer supported.

Author: 5cript

stringify/jss_optional.h

@@ -0,0 +1,86 @@
+#ifndef JSS_OPTIONAL_H_INCLUDED
+#define JSS_OPTIONAL_H_INCLUDED
+
+#include "tmp_util/fundamental/eval_if.hpp"
+#include "tmp_util/fundamental/is_same.hpp"
+#include "tmp_util/fundamental/null_type.hpp"
+
+// really want to swap with std::optional
+#include <boost/optional.hpp>
+
+namespace JSON
+{
+    namespace Internal
+    {
+        template <typename T>
+        struct has_value_type {
+            typedef char yes[1];
+            typedef char no[2];
+
+            template <typename C>
+            static yes& test(typename C::value_type*);
+
+            template <typename>
+            static no& test(...);
+
+            constexpr static const bool value = sizeof(test<T>(nullptr)) == sizeof(yes);
+            using type = mplex::bool_ <value>;
+        };
+
+        template <typename T>
+        using has_value_type_t = typename has_value_type <T>::type;
+
+        struct get_value_type
+        {
+            template <typename T>
+            struct apply
+            {
+                using type = typename T::value_type;
+            };
+        };
+
+        template <typename T>
+        struct is_optional
+        {
+            using __value_type = mplex::eval_if_default_t <has_value_type_t <T>, mplex::null_t, get_value_type, T>;
+            using type = mplex::eval_if_default_t <
+                mplex::bool_ <!std::is_same <__value_type, mplex::null_t>::value>,
+                mplex::false_,
+                mplex::is_same,
+                T,
+                boost::optional <__value_type>
+            >;
+            constexpr static const bool value = type::value;
+        };
+
+        template <typename T, bool _is_optional>
+        struct is_optional_set_impl
+        {
+            static inline bool isSet(T&&) noexcept { return true; }
+        };
+
+        template <typename T>
+        struct is_optional_set_impl <T, true>
+        {
+            static inline bool isSet(T&& t) noexcept { return t.operator bool(); }
+        };
+
+        template <typename T>
+        inline bool is_optional_set(T&& t) noexcept {
+            using decayed = typename std::decay <T>::type;
+            return is_optional_set_impl <T, is_optional <decayed>::value>::isSet(std::forward <T> (t));
+        }
+    }
+
+    template <typename T>
+    std::ostream& stringify (std::ostream& stream, std::string const& name, boost::optional <T> const& value, StringificationOptions const& options = DEFAULT_OPTIONS)
+    {
+        // only write if actually existing
+        if (value)
+            return stringify (stream, name, value.value(), options);
+        else
+            return stream; // do nothing
+    }
+}
+
+#endif // JSS_OPTIONAL_H_INCLUDED